Transformer Driver for
Isolated RS-485 Interface
MAX253
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 6, V
IN
= 5V ±10%, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(FS = HIGH)
plot09
OUTPUT VOLTAGE vs. LOAD CURRENT
(FS = LOW)
plot10
OUTPUT VOLTAGE vs. LOAD CURRENT
(FS = HIGH)
9
8
OUTPUT VOLTAGE (V)
CIRCUIT OF FIGURE 7
V
IN
= 3.3V
TURNS RATIO = 1:2.1
CIRCUIT OF FIGURE 6
V
IN
= 5.0V
TURNS RATIO = 1:1.3
plot11
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
V
IN
= 4.5V
V
IN
= 5.5V
10
9
8
OUTPUT VOLTAGE (V)
7
6
5
4
3
2
1
0
CIRCUIT OF FIGURE 6
V
IN
= 5.0V
TURNS RATIO = 1:1
CIRCUIT OF FIGURE 7
V
IN
= 3.3V
TURNS RATIO = 1:2.1
CIRCUIT OF FIGURE 6
V
IN
= 5.0V
TURNS RATIO = 1:1.3
10
7
6
5
4
3
2
CIRCUIT OF FIGURE 6
V
IN
= 5.0V
TURNS RATIO = 1:1
MEASURED AT TP1
0 20 40 60 80 100 120 140 160 180 200 220
LOAD CURRENT (mA)
1
0
MEASURED AT TP1
0 20 40 60 80 100 120 140 160 180 200 220
LOAD CURRENT (mA)
20 40 60 80 100 120 140 160 180 200
LOAD CURRENT (mA)
SWITCHING WAVEFORMS
(TWO CYCLES)
SWITCHING WAVEFORMS
(BREAK BEFORE MAKE)
D1
D1
D2
D2
CIRCUIT OF FIGURE 1
CIRCUIT OF FIGURE 1
TIME FROM SHUTDOWN TO POWER-UP
SD
TP1 (OUTPUT VOLTAGE)
CIRCUIT OF FIGURE 6
4
_______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
